Snežana Pavlović

Parasitic mycobiota of yellow gentian (Gentiana lutea L.).

Mycopopulation of yellow gentian growing in plantations was studied in 2008 and 2009. Fourteen species of fungi were registered at seed, out of which five were pathogenic. The most common species was Alternaria alternata (72-74 %). Species of the genus Fusarium (F. oxysporum, F. solani and F. equiseti) were present in a small percentage (2-6 %). These species, as well as F. verticillioides, were isolated from root, and Fusarium sp. was isolated from the flowers. Alternaria alternate, Epicoccum purpurescens, Phoma sp. and Alternaria sp. were regularly present on the leaves and stems.

PATHOGENIC, MORPHOLOGICAL AND MOLECULAR CHARACTERISTICS OF ALTERNARIA TENUISSIMA FROM SOYBEAN

During 2008 and 2009 phytopathological isolations were done from soybean plants and seed samples from several localities in Serbia. A total of 19 isolates of Alternaria spp. were isolated, 13 from the seed and 3 from both leaf and stem. In order to determine and characterize isolates, cultural, morphological, molecular and pathogenic characteristics were thoroughly investigated. The slowest growth of the examined isolates was noted on Malt agar (MA) with average colony diameter of 42.9 mm after 7 days of incubation. On other two media (V8 and PCA), colony growth was uniform and faster, with average diameter of 66.8 mm and 66.1 mm, respectively. Isolates of fungi form unbranched or poorly branched conidial chains on short unbranched conidiophores. Conidia are dark in colour, multicellular with transverse and longitudinal septae. They are of different size regarding the place of formation in the chain. Based on these characteristics, the tested isolates were determined as Alternaria tenuissima. Molecular identification with sequencing of ITS1-5.8S-ITS2 rDNA verified that investigated isolates belong to Alternaria tenuissima group. Pathogenicity test proved that all isolates were more or less virulent to soybean seed (12.5% to 40% of rotten seeds), while pathogenicity on plants was poorly expressed.

Antifungal activity of Pseudomonas chlororaphis Q16 against Sclerotinia sclerotiorum isolated from different medicinal plants

Phytopathogenic fungi Sclerotinia sclerotiorum is very destructive pathogen of the stem of many medicinal plants. Because the use of pesticides is forbidden during production of medicinal plants, presence of S. sclerotiorum may produce serious loss. The use of PGP (Plant Growth Promoting) bacteria, for which have been demonstrated to show antifungal activity with varying degrees of antagonism, gives protection to medicinal plants. The antifungal activity of different fractions of P. chlororaphis Q16 culture was examined on 6 representative isolates of S. sclerotiorum from medicinal plants: nettle, cumin, marshmallow, valerian and two strains of Echinacea. The highest efficacy of mycelial growth inhibition showed heat stabile antifungal factor with growth inhibition range from 52.75% (marshmallow isolate) up to 83.36% (isolate from E. purpurea). The inhibition of mycelial growth was similar for all S. sclerotiorum isolates when 24h culture was performed and ranged from 60.28% (cumin isolates) to 76.47% (nettle isolates).

Gibberella intermedia the pathogen of St. John's wort, coneflower and marshmallow in Serbia.

Gibberella intermedia (Kuhlmann) Samuels et al. (anamorf: Fusarium proliferatum /Matsushima/ Nirenberg) was isolated from seeds of St. Johns wort, marshmallow, and coneflower, as well as from roots and stalks of marshmallow and roots of coneflower. These plants had symptoms of leaf chlorosis, malformation, withering and plant dwarfing and were collected from several localities in Serbia during five-year investigations of mycopopulations of the mentioned plants. The morphological characteristics of the pathogen were described.